LONDON — Telecom giant Vodafone has agreed to buy Liberty Global’s operations in Germany, the Czech Republic, Hungary and Romania in a deal valued at 18.4 billion euros ($21.8 billion) as the industry moves toward “next-generation” technology carrying voice, data and video over a single network. Vodafone says the transaction will help it become “the leading next-generation network owner in Europe,” with a total reach of 110 million homes and businesses.